1. Field of the Invention
The present invention relates to a steering wheel assembly and in particular to a structure for mounting a steering wheel assembly on a steering shaft.
2. Description of Related Art
A steering wheel assembly comprises a wheel or annular gripping ring portion, a pad portion disposed in the center of the ring portion, and a plurality of angularly spaced apart spokes for connecting the ring portion with the pad portion. A separated or independent pad is mounted at the pad portion.
A ring core is embedded in the ring portion and, similarly, spoke cores are embedded in the respective spokes. In this case, the ring and spoke cores are each covered with a covering layer made, for example, of foamed polyurethane, such as TPE. Further, a boss plate with a boss for mounting the entire steering wheel assembly on a steering shaft is coupled to the spoke cores beneath the pad adjacent the pad portion.
On the other hand, a steering wheel assembly has been proposed which has no interface line between the covering layers of the spokes and the pad portion when the covering layers and the pad portion are integrally formed in order to improve the appearance of the finished product (e.g., Japanese Unexamined Utility Model Publication No. Hei. 2-133955).
Although such type of steering wheels in which the ring and spoke core covering layers are integral with the pad portion have been widely used owing to its improved appearance, they have a problem, which will be described below, when mounting the steering wheel assembly on the steering shaft. Since the pad can not itself be removed from the covering layer for the ring core and spoke cores in the above-mentioned type of steering wheel assembly, it is hard to conduct screw-fastening of the boss plate to the steering shaft, especially when the boss plate is connected by a nut. Accordingly, a novel steering wheel assembly has been demanded which can be easily and positively mounted on the steering shaft even when the boss plate is connected with the spoke cores, that is, after the steering wheel has been assembled.
It is, therefore, an object of the present invention to provide a novel steering wheel assembly, including a cover layer covering a ring core and spoke cores which is formed integrally with a pad portion, that can be easily and positively mounted on a steering shaft.